Hi Bart, Avri, May I know if you have any suggestion for this RFC fix? Very appreciated : ) On Mon, 2020-07-06 at 21:22 +0800, Stanley Chu wrote: > Currently I/O request could be still submitted to UFS device while > UFS is working on shutdown flow. This may lead to racing as below > scenarios and finally system may crash due to unclocked register > accesses. > > To fix this kind of issues, specifically quiesce all SCSI devices > before UFS shutdown to block all I/O request sending from block > layer. > > Example of racing scenario: While UFS device is runtime-suspended > > Thread #1: Executing UFS shutdown flow, e.g., > ufshcd_suspend(UFS_SHUTDOWN_PM) > Thread #2: Executing runtime resume flow triggered by I/O request, > e.g., ufshcd_resume(UFS_RUNTIME_PM) > > This breaks the assumption that UFS PM flows can not be running > concurrently and some unexpected racing behavior may happen. > > Signed-off-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx> > --- > drivers/scsi/ufs/ufshcd.c | 38 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > index 59358bb75014..104173c03492 100644 > --- a/drivers/scsi/ufs/ufshcd.c > +++ b/drivers/scsi/ufs/ufshcd.c > @@ -158,6 +158,12 @@ struct ufs_pm_lvl_states ufs_pm_lvl_states[] = { > {UFS_POWERDOWN_PWR_MODE, UIC_LINK_OFF_STATE}, > }; > > +#define ufshcd_scsi_for_each_sdev(fn) \ > + list_for_each_entry(starget, &hba->host->__targets, siblings) { \ > + __starget_for_each_device(starget, NULL, \ > + fn); \ > + } > + > static inline enum ufs_dev_pwr_mode > ufs_get_pm_lvl_to_dev_pwr_mode(enum ufs_pm_level lvl) > { > @@ -8588,6 +8594,19 @@ int ufshcd_runtime_idle(struct ufs_hba *hba) > } > EXPORT_SYMBOL(ufshcd_runtime_idle); > > +static void ufshcd_cleanup_queue(struct scsi_device *sdev, void *data) > +{ > + if (sdev->request_queue) > + blk_cleanup_queue(sdev->request_queue); > +} > + > +static void ufshcd_quiece_sdev(struct scsi_device *sdev, void *data) > +{ > + /* Suspended devices are already quiecsed and shall be skipped */ > + if (!pm_runtime_suspended(&sdev->sdev_gendev)) > + scsi_device_quiesce(sdev); > +} > + > /** > * ufshcd_shutdown - shutdown routine > * @hba: per adapter instance > @@ -8599,6 +8618,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle); > int ufshcd_shutdown(struct ufs_hba *hba) > { > int ret = 0; > + struct scsi_target *starget; > > if (!hba->is_powered) > goto out; > @@ -8612,7 +8632,25 @@ int ufshcd_shutdown(struct ufs_hba *hba) > goto out; > } > > + /* > + * Quiesce all SCSI devices to prevent any non-PM requests sending > + * from block layer during and after shutdown. > + * > + * Here we can not use blk_cleanup_queue() since PM requests > + * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent > + * through block layer. Therefore SCSI command queued after the > + * scsi_target_quiesce() call returned will block until > + * blk_cleanup_queue() is called. > + * > + * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can > + * be ignored since shutdown is one-way flow. > + */ > + ufshcd_scsi_for_each_sdev(ufshcd_quiece_sdev); > + > ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM); > + > + /* Set queue as dying to not block queueing commands */ > + ufshcd_scsi_for_each_sdev(ufshcd_cleanup_queue); > out: > if (ret) > dev_err(hba->dev, "%s failed, err %d\n", __func__, ret);